In a pressure regulator, since inlet pressure acts on a valve seat to produce an additional force which directly influences the performance of a pressure regulator product, a balancing valve spool is usually employed.
FIG. 1 shows a prior art balancing valve spool. In this spool, one end of an n-shaped diaphragm 10 is fixedly connected with a valve rod and the other end of the n-shaped diaphragm is fixedly connected with a valve body or a connecting piece (for connecting the valve body with an actuator), wherein the end of the n-shaped diaphragm which is connected with the valve rod needs to be fixed on the valve rod by using a fixing piece. From FIG. 1, it can be seen that this balancing valve spool has a complex structure, with a large number of parts, resulting in relatively higher cost.
FIG. 2 is another prior art balancing valve spool. This design adopts a valve rod mobile piston structure, wherein an O-ring 20 is arranged on a piston sleeve 12 to achieve a sealing effect, isolating inlet pressure and outlet pressure. However, this kind of structure is not beneficial for guiding a valve rod 11 (since the O-ring 20 has elasticity, the valve rod 11 will shake). In addition, the smoothness of a cylindrical surface of the piston sleeve 12 in contact with the O-ring is difficult to guarantee. Further a guide sleeve 30 needs to be added to guide the valve rod 11 and additional space needs to be added in a longitudinal space of the valve in order to install the guide sleeve 30 and, thereby, the structure of the valve is more complex.